How to determine which Ubuntu flavor I'm on?

I am on Xubuntu (16.04, btw) however lsb_release -a gives me: user@host:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.3 LTS Release: 16.04 Codename: xenial Should it display Xubuntu, or is this legit output? And if it is, how can I (by the CLI) know the exact Ubuntu distro I'm on? And what does the warning No LSB modules are available. mean anyway? (It is output to *stderr*: user@host:~$ lsb_release -a >/dev/null No LSB modules are available. so I'm guessing in nominal case it shouldn't be there)